Tobacco smoke filters made of paper



United States PatentQifice 3,400,723 Patented Sept. 10, 1968 3,400,723TOBACCO SMOKE FILTERS MADE OF PAPER Paul Adolf Miiller, Triesenberg,Liechtenstein, and Erich Barkowski, Aschaffstrasse 69, Aschafienburg,Germany No Drawing. Filed Feb. 20, 1967, Ser. No. 617,084 Claimspriority, application Switzerland, Feb. 23, 1966, 2,626/ 66 14 Claims.(Cl. 131-467) ABSTRACT OF THE DISCLOSURE v Tobacco smoke filters,especially for filter-tip cigarettes, which do not impart a so-calledpaper taste to tobacco smoke passing therethrough in which the paper issubstantially free of sulphurous compounds and ismade from a pulp intowhich is added a sulphur-free metallic compound of an acid from thegroup comprising acetic acid, propionic acid and formic acid in anamount to achieve a pH value less than 6.0 in the water container of thelast screen of the paper-making machine. The compound preferably isaluminum acetate.

The present invention relates to improvements in tobacco smoke filtersmade of paper, particularly for filtertip cigarettes, in paper for suchfilters and in methods for producing such filters. More particularly,this invention relates to improving the taste qualities of such filters.

Filters containing paper are known and widely used for filter-tipcigarettes. One method, which is now practiced, for treating paper tomake it into an efficient filtering material, i.e., filter paper forfilter-tip cigarettes, includes passing a web of smooth raw paperbetween at least one pair of intermeshing grooving or corrugating rollsprovided with axially spaced circumferential ribs. The rolls form in thepaper a corresponding number of parallel grooves, i.e. corrugate thepaper. During treatment by the rolls, the engagement of the ribs withthe paper prevents any substantial transverse shrinking or gatheringthereof so that, as a result, the paper web is stretched laterally. Suchstretching loosens the fibers of the paper to form fuzzy areas withnumerous projecting fiber ends on the surfaces of the grooved web atlocations where the fibers are at least partially separated or pulledapart. In some cases the stretching may be to such an extent as to causehaphazardly-located, discontinuous longitudinal tears which have frayedfuzzy edges, although the web for all practical purposes substantiallyretains its transverse continuity.

This method of treating paper to render it more effective as a tobaccosmoke filter is well known, as well as filter paper produced by suchtreatment, and filter rods or plugs made by laterally gathering suchfilter paper into an endless string or cord which is wrapped and thencut into filter rods or plugs of any desired length. Such method andproducts are disclosed, for example, in the following US. patents: Nos.2,916,039; 2,931,748; 2,995,481; 3,161,557; 3,179,024; 3,226,280.

In accordance with the principal method used to date for grooving andlaterally stretching smooth raw paper to the extent needed for efiicientfiltering without completely destroying the lateral or transversecontinuity of the web it is necessary, prior to the grooving treatment,to make the paper web soft or yielding by a suitable treatment e.g. bymoistening with water or any other suitable liquid. As a result, thegrooved and laterally stretched web must be dried after the corrugatingand stretching treatment before being wound up on spools or bobbins, orbefore being made directly into filter rods or plugs. This knowntreatment method includes before, during or after the drying treatment,further deformation or mechanical working of the corrugated andstretched web by any appropriate device, for example, by pinch rollshaving smooth or knurled surfaces which partially compress or flattenthe corrugations and so minimize the existence of unobstructed throughpassages in filters made of such paper or greatly restrict suchpassages. The thus produced filter paper may be wound on spools orbobbins to be fed later to filter rod machines of well known design, ormay be fed directly into a filter rod machine. In the abovedescribedknown grooving and stretching method, it also is advantageous to heatthe grooving and stretching rolls to a temperature up to several hundredF. though cold rolls are by no means insufficient.

Although the known treatment method, as described above, requires thepaper to be quite moist during the grooving and stretching process, thismoistening is not absolutely necessary. Smooth raw paper webs of sometypes be treated by passing through the nip of a pair of suchintermeshing grooving or corrugating rolls without advance moistening.As so treated in the dry the paper web shows less distinctive or nolongitudinal grooves but for lower grade demands of filtering qualitiesand of end face appearance, when made into a cigarette filter, suchpaper web treatment is commercially applicable and offers the advantageto omit any moistening and drying devices.

It may be pointed out that other means than the above explained pairs ofgrooving rolls are known for treating a paper web to produce fiberloosening and projecting fiber ends to render it more effective for useas a filtering material. For example, rolls provided with prongs ofdetermined shape are sufficient for producing slot-like openings ofdesired shapes in a paper web treated with such rolls so that adheringstruck out parts of the paper have frayed edges with a multitude ofprojecting fiber ends, as disclosed in US. Patent 2,847,286. It has beensuggested also to produce lacerations haphazard in shape and size bypassing a dry paper web through the nip between two intermeshing sets ofaxially-aligned and axially-spaced toothed discs as well as through thenip between a smooth soft rubber roll and a metal roll provided withaxially-spaced circumferential ribs.

All cigarette filters made heretofore from paper webs, irrespective oftheir treatment to render them a more efficient filtering material, havethe disadvantage, especially in cigarettes of light and mild tobaccomixtures, of producing a taste in the smoke which is well known tocigarette manufactures as paper taste. It is believed that this papertaste is not produced by substances given off from the paper filter intothe smoke stream passing therethrough but rather by an absorption ofsmoke components in a different degree from filters of other material,especially cellulose acetate fibers. But the existence of a paper tasteaccompanying paper filters used with sensitive, i.e. light and mild,tobacco mixtures is a fact which is regarded occasionally by cigarettemanufacturers as a deficiency.

While the cause of such paper taste is not known, it has been thoughtthat the above-described moistening and drying steps, and the engagementof the moist paper with the hot metallic grooving and stretching rolls,may possibly be somewhat responsible. Tests have been shown, however,that paper filters made from a paper web treated, when dry, bynon-metallic means to render it more effective as a filter for tobaccosmoke have met with failure in respect to elimination or minimization ofthe paper taste.

Additionally, prior to this invention attempts have been made alongother lines to reduce or eliminate the socalled paper taste attendantcigarette filters made of paper. Such efforts have included the additionof acid substances to the fluid used to moisten the paper as apreliminary to the grooving and streaching treatment. In

other cases, acid substances have been sprinkled onto the moistened web,either in advance of or subsequent to the grooving treatment, and insome instances have been sprinkled on the grooved web after it has beendried. Such substances have included acetic acid, formic acid, aluminouswater and other acidic substances. All such attempts have met withfailure, however, because paper webs treated with such substances, havea disagreeable odor and, moreover, tend to corrode metal parts of thegrooving or lacerating apparatus or otherwise deleteriously affect itsoperation. Unsuccessful earlier efforts to reduce or eliminate the papertaste also have included the use of raw paper having a pH value lowerthan its normal value of 6.1 to 6.3. All such papers heretofore used,however, have not been satisfactory because they frequently have ayellow color, which is most unattractive to smokers, or have a reducedflexibility that renders them somewhat brittle and of a straw-likecharacter. The brittle characteristic makes such paper completelyunsatisfactory for a fiber loosening treatment, as aforesaid, so thatsuch paper webs usually are ineffective as a filter material for tobaccosmoke and furthermore have no appreciable reduction in the paper taste.

It is, therefore, an object of this invention to provide improved filterpaper for use in the filters of filter-tip cigarettes and filter rods orplugs made therefrom, which, when in use, has a greatly reduced ornegligible paper taste.

It is another object of this invention to provide a paper web made froma sulphur-free paper pulp into which is added a sulphur-free metalliccompound of an acid from the group comprehending acetic acid, propionicacid and formic acid in an amount to achieve a pH-value less than 6.0 inthe water container of the last screen of the papermaking machine, andthe paper web then is corrugated and/or lacerated in a controlled mannerto loosen its fibers, wrapped up, reshaped into an endless paper rope orfilter cord of approximative round sectional shape and subdivided intofilter portions of desired lengths.

Another object of this invention is to provide a tobacco smoke filter,which is made by subdividing an endless filter rope or cord containingpaper in a wrapper and having an approximative round sectional shape,and wherein the paper is free from sulphurous compounds and contains ametallic compound of an acid from the group comprehending acetic acid,propionic acid and formic acid.

Other objects and advantages of the invention will become apparent fromthe following description.

Known tobacco smoke paper filters are normally made from raw paper,preferably of a weight of from about 20 to about 40 grams per squaremeter. During manufacture of such raw paper aluminum sulfate isincorporated into the paper pulp in order to increase the tensilestrength of the dried paper. Aluminum sulfate has the property ofsomewhat increasing the coherence or adhesion of the fibers constitutingthe paper web. When such paper is used as a filter in filter-tipcigarettes containing light and mild tobacco mixtures the undesiredso-called paper taste is imparted to the tobacco smoke.

It has been discovered and proved by a multitude of tests that the papertaste normally attendant paper filters is reduced or completelyeliminated by this invention. To this end the raw paper web should beproduced from a pulp substantially free from sulphuric compounds andcontaining no aluminum sulfate. To achieve the necessary glueing oradhesion and coherence of the fibers in the paper web other suitablecompounds have to be substituted, for aluminum sulfate in the pulp,which possess the same desired property as aluminum sulfate in thisregard but which have no sulphurous components. It has been found thataluminum acetate for example, is such a suitable compound whensubstituted in an amount such that the pH-value of the water in thecontainer of the last screen of the paper-making machine is reduced to avalue less than 6.0 or preferably less than 5.8. To accomplish this thealuminum acetate comprises from about 1% to about 2% by weight of thepulp. Such a paper Web, substantially free of sulphurouscompounds andhaving a higher acid content than normally, can be corrugated orlacerated by a fiber-loosening treatment in dry or moistened conditiontoany desired extent and wound up on spools or bobbins which are made upinto filter plugs later on, or may be fed directly into a filter rodmachine for wrapping and forming in an endless filter rope which issubdivided into filter rods and/ or plugs of desired lengths.

The corrugated and/or lacerated paper webs produced continuously by theabove described method can be easily made up into filters which possessmechanical qualities, for example tensile strength and dimensionalstability, at least equivalent to the corresponding qualities of filtersmade of hitherto used paper webs. Also the raw paper embodying thisinvention has been found to possess mechanical qualities at leastequivalent, and possibly better, than corresponding qualities ofhitherto used raw paper. The following table compares relevantcharacteristics of the best quality raw paper used heretofore for makingfilter paper according to the above-described known process with rawpaper embodying this invention.

COMPARISON OF QUALIIIES OF RAW PAPER USED HERE- TOFORE TO MAKE FILTERPLUGS WITH RAW PAPER ACCORDING TO THIS INVENTION It is evident from theforegoing table that raw paper for filters according to this inventionhas better mechanical qualities than raw paper used heretofore fortobacco smoke filters.

Filter-tip cigarettes have been prepared equipped with filters fromlongitudinally grooved, mutilated and lacerated paper Webs produced frompaper according to this invention and having values according to theabove table for socalled blind smoking tests by experts. These testsdemonstrated that the paper taste hitherto common to cigarettes havingpaper filters is noticeable only to a negligible extent or not at allwith filters embodying this invention. Further tests have shown thatthis phenomenon probably results from the fact, that in the paper andits cellulose fibers the aluminum sulfate is replaced by aluminumacetate and at the same time the grooved and/ or lacerated paper web isprovided with a higher acid content. Without doubt the described filtersprovide a' noticeable improvement in taste qualities compared to allother known paper filters for cigarettes.

Other tests have proved that a further reduction of the pH-value below5.8 to about 5.4 completely removes all eventual existing remainders ofthe paper taste and is accompanied by a further taste improvement. Anincrease of the acid content in the paper up to a range of pH values offrom about 5.2' to about 5.0 does not produce any taste disadvantage;but the preferred range of pH values with this kind of paper'filter isfrom about 5.6 to about 5.3.

Extended tests have been made with filters made of paper webs having acomplete replacement of thehitherto used aluminum sulfate byaluminumacetate according to the following Examples I and II,respectively.

Example I Into the beater containing paper pulp prepared according towell known methods but without any aluminum sulfate has been passedliquid aluminum acetate Al (OH) (CH COO) in small amounts whilstmonitoring the pH value of the water in the container of the last screenof the paper-making machine. The addition of Al (OH) (CH COO) wascontinued until further addition no longer reduced the pH value, whichcondition was reached in the range of pH=5.8 to 5.6. A raw paper web ofabout 32 to 34 grams weight per square meter and with a cloudy"structural appearance was produced from such pulp and Wound up into araw paper roll.

From this raw paper roll a paper web was continuously wound off with aspeed of about 60 to 100 cm. per second, moistened, passed through thenip between a pair of heated rotating steel rolls provided withinterfitting axially-spaced circumferential ribs to stretch the paperlaterally and then dried by passing a heated dryer.

The treated paper web was provided with narrow longitudinal ridges,intermediate longitudinal grooves, i.e., a corrugated structure, and amultitude of irregularly distributed disconnected longitudinal tears.The web was fed into a filter rod machine of known design, gatheredlaterally to an endless rope of about 8.3 mm. diameter, wrapped, andsubdivided into filter rods of desired length.

The filters produced according to Example I were attached to cigarettesand checked in respect to the nicotine and tars absorption as well as tothe taste quality and compared to filters having the same drawresistance made from aluminum sulfate containing raw paper of the sameweight treated in the same manner. The filtering effect of theacetate-containing paper filter is at least of the same value andaccording to many test results even higher than the sulfate-containingpaper filter. The taste improvement of this acetate containing paperfilter compared to sulfate containing paper filter has been provedbeyond any doubt by so-called blind smoking tests of experts.

Example 11 The pulp in the beater was prepared as in Example I andaluminum acetate AI (OH) (CH COO) added up to a pHvalue in the water ofthe container of the last screen of about 5.8 to 5.6. Then dilutedacetic acid CH COOH was admixed with the pulp up to a pH-value of thewater from the last screen of about 5.4. The production of paper websand filters was then carried out as described in Example I.

Filter plugs of 20 mm. length prepared according to Example 11 wereattached to a tobacco column of 65 mm. length and tested and compared tofilter plugs of the same length and identical draw resistance made fromcellulose acetate fibers (Typ ESTRON 3.340) connected to identicaltobacco colums. The filter plugs containing cellulose-acetate fiberswere prepared in a known manner together with Driacetin as a softeningagent whilst the filter plugs according to Example II were used withoutany additional preparation. The filtering efiiciency of the two filterplu-g types was checked and the following values of components in thesmoke stream of one cigarette were found:

Miligrams Milligrams nicotine solid substances Cigarette with filterExample II 0.8 16 Cigarette with cellulose-acetate filter 1. 2 21 plugs.

It may be pointed out that paper webs and filter plugs producedaccording to Examples I and II are completely odorless and insipid. Notrace of an odor exists in closed rooms used for long time storing ofraw paper, treated paper webs and filter rods produced according to thisinvention in contrast to the objectionable odor accompanying filter rodswhich are made from raw paper impregnated subsequent its production withacid liquids as described above. Also the grooving and laceratingtreatment of raw paper produced as described in Examples I and II, bypassing between heated metal rolls subsequent to a tmoistening step andfollowed by a drying step, can be carried out without any odorindicating the presence of acetic compounds or acetic acid added into apulp. Moreover no corrosion of metallic parts exists whilst raw paperembodying this invention is in contact therewith while' being treated insuitable devices.

A quantitative chemical analysis to ascertain the critical substances inthe raw paper or filter rods is rather difficult but suitable methodsfor a qualitative examination are available. For a detection of aluminumsulfate normally contained in paper filters, but not allowable accordingto this invention, an examination using chloride of barium is preferredwhich shows in known manner a deposit of barytes (barium sulfate) ifsulfate compounds are contained in the paper. The qualitative detectionof acetic compounds in paper filters is more difficult but possibleusing the known Kadodyl check or the potassium bisulphate check. Thefirst mentioned check is performed by a reaction of arsenic trioxyd andthe presence of acetates is indicated by an odor of garlic. The secondmentioned check results in a typical acetic acid odor.

Consequently the lack of sulfates and the presence of acetates in apaper web and in paper filter plugs can be positively substantiated andconstitute material features of the products with satisfactorydistinctness.

The above described examples and embodiments of the present method aswell as the products thereof relate to a replacement of aluminum sulfatenormally contained in paper webs by aluminum acetate with or withoutadditional acetic acid. It may be pointed out, however, that the presentmethod and the products thereof are not restricted to the mentionedreplacement substances. An improvement of paper filter taste qualitiescan be achieved also by replacing aluminum sulfate in paper webs byother aluminum compounds of sulphur-free monovalent organic carbon acidsas for example formic acid HCOOI-I or propionic acid C H COOH. The tastequalities of paper filters are also improved when aluminum sulfate isreplaced by calcium acetate or magnesium acetate or other calcium ormagnesium compounds of sulphur-free monovalent organic carbon acids, butsuch a replacement also influences mechanical and other properties ofthe paper.

We claim:

1. A tobacco smoke filter, especially for filter tip cigarettes,generally in the shape of a cylindrical plug longitudinally permeable togases and a consisting essentially of paper, characterized in that thepaper is substantially free of sulphurous compounds and containsaluminum acetate as a substitute for aluminum sulfate sizing agent.

2. A tobacco smoke filter according to claim 1, characterized in thatthe paper contains the aluminum acetate in a small percentage of thepaper weight not exceeding about 2% by weight.

3. A tobacco smoke filter according to claim 1, characterized in thatthe pH-value of the paper is less than 6.0.

4. A tobacco smoke filter according to claim 1, characterized in thatthe pH-value of the paper is less than 5.8.

5. A tobacco smoke filter according to claim 1, characterized in thatthe pH-value of the paper is in the range of from about 5.6 to about5.3.

6. A tobacco smoke filter according to claim 1, characterized in thatthe paper has a weight of from about 20 to about 40 grams per squaremeter.

7. A tobacco smoke filter according to claim 1, characterized in thatthe fibers of the paper are loosened and at least partly pulled apartand the paper is covered by projecting fiber ends.

8. A tobacco filter plug according to claim 1, characterized in that thepaper comprises a transversely gathered sheet having a corrugatedstructure in transverse section.

9. Tobacco smoke filter fibrous sheet material consisting essentially ofporous, smoke permeable paper substantially free of sulphurous compoundsand containing aluminum acetate as a substitute for aluminum sulfatesizing agent.

10. Fibrous sheet material according to claim 9 characterized in thatthe paper contains the aluminum acetate in a small percentage notexceeding about 2% by weight of the pulp from which the paper was made.

11. Fibrous sheet material according to claim 9 characterized in thatthe pH-value of the paper is less than 6.0, as measured by the water inthe container for the last screen of the machine on which the paper wasmade.

12. Fibrous sheet material according to claim 9 characterized in thatthe pH-value of the paper is less than 5.8, as measured by the water inthe container for the last screen of the machine on which the paper wasmade.

13. Fibrous sheet material according to claim 9 characterized in thatthe pH-value of the paper is in the range of from about 5.6 to 5.3, asmeasured by the water in the container for the last screen of'themachine on which the paper was made.

14. Fibrous sheet material according to claim 9 characterized in thatthe paper has a weight of from about 20 to about 40 grams per squaremeter.

References Cited UNITED STATES PATENTS 1,808,068 6/1931 Rafton 1621812,711,371 6/1955 Lurie 162-181'X 2,847,086 8/1958 Muller 131--216 X2,995,481 8/1961 Muller 131261 X 3,049,468 8/1962 Hinton et a1 162181 X3,128,223 4/1964 Rosenberg et al 1 62-181 FOREIGN PATENTS 1,022,513 1/1958 Germany.

745,245 2/1956 Great Britain.

SAMUEL KOREN, Primary Examiner.

D. J. DONOHUE, Assistant Examiner.

